Studies
by Boeing engineers have helped NASA keep the International Space Station
viable for the foreseeable future.

After the U.S. Space Shuttle Columbia accident on Feb. 1, NASA asked
engineers at Boeing NASA Systems in Houston, part of Integrated Defense
Systems, to look at options to maintain a safe and operable ISS.

The team, which includes a group called VIPeR, or Vehicle Integrated
Performance and Resources, has taken into account the delay of the unique
cargo-ferrying capabilities of the space shuttle.

As such, the team has had to rely on Russian vehiclesSoyuz and Progressas
the only means of transporting cargo to the ISS until the shuttle returns
to flight or the European Space Agency's Automated Transfer Vehicle is
available.

The Boeing team has focused primarily on a smaller ISS crewtwo people
rather than threeand the need for spare hardware. Working closely with
NASA's ISS mission integration group, the Boeing team has tracked the
primary consumables used by the station and its crew, and has conducted
analyses to balance ISS supply and return requirements with vehicle performance
and research.

The VIPeR team has focused primarily on station propellant, which keeps
the ISS in the proper orbit and orientation and has been one of the most
critical consumables in past studies. The team concluded that planned
Progress launches will meet propellant resupply needs.

The next critical consumable is water to support the crew and system.
A crew member uses about two kilograms of water a day for drinking, food
and oxygen generation. The Boeing team has looked at how water can be
brought up and has examined ways to reduce water needs.

A significant area of study is the number of crew members on board the
ISS.

"We looked at how long we could leave three crew members up there and
when we would go to two crew members," said Neil Lemmons, senior systems
engineer with the Boeing VIPeR team.

"Without the space shuttle, it was quickly determined by all involved
that a three-person crew could not be sustained," said Bob Korin, manager
of the VIPeR team. Keeping a crew on the ISS is important, he added, because
it would "give us a set of eyes, hands and creative thinking capability
to respond to things that arise."

The Boeing team, backed by a strong effort from the safety community,
has concluded that no significant safety issues are associated with a
two-person crew.

Although there would be some limits, a two-person crew could continue
to keep scientific research going and maintain support for preventive
and corrective maintenance, anomaly investigation and response, and other
ISS system operations needs.

Boeing and NASA engineers have studied the impact of a two-person crew
on future science research.

"The focus has been on new samples and consumables for the science and
research apparatus already on board the ISS that require minimal space
and weight," said Rick Golden, program manager of ISS payload integration.

"Our group (Boeing and its subcontractors, Teledyne Brown Engineering
and United Space Alliance) ensures that interfaces between the science
experiments and the space station are compatible," Golden said.

"A lot of our focus has been working the safety aspects to fly U.S. payload
hardware on Soyuz and Progress launches," Golden explained. "We are positioning
a select number of payloads at the Baikonur launch site in order to be
able to take advantage of any space that becomes available on upcoming
Progress flights."

The Boeing ISS team has reassessed the manifests for several planned
shuttle launches. "We had to support system maintenance which may have
required changing out filters, valves, bags and things along those lines
or other items to support system repair," Korin said.

The team has come up with a prioritized shopping list of what could be
taken up without the space shuttle. This includes the amount of propellant,
water, gas, and dry cargo needed to support the ISS and its crew. The
ISS subsystem teams, including the logistics and maintenance team, have
played a critical role in defining the shopping list of needed items.

The Environmental Control and Life Support System group has identified
the selector valve and filter for the Carbon Dioxide Removal Assembly,
and the Internal Thermal Control System group has identified the Pump
Package Assembly as essential spares to be manifested on Russian Soyuz
and Progress flights.

The Soyuz is the ISS crew escape vehicle used in case of emergency. It
is certified for 200 days of life and is rotated every 180 to 190 days.
Soyuz vehicles are normally taken to the ISS by a taxi crew" that brings
the "old" one back. The Progress vehicle is unmanned and carries crew
supplies and hardware spares to help maintain the life of the ISS. There
are normally three Progress flights a year.

"The Russians have given us about a 30-kg (66-lb.) allocation for U.S.
items to be launched on Soyuz 6S, so we have been working very hard with
NASA to make sure all these items are certified to be launched on a Russian
vehicle and the Russians properly stow them for launch," said Ray V. Gonzales,
Boeing launch package manager for Russian vehicles. "We are also working
to get these items to Moscow and then to Baikonur, Khazakstan, where they
will be launched."